Octane 101 - Motorcycle Gas
What Is An Octane Number, And What Does It Mean? And What Octane Rating Do You Really Need?John Lavina (February 2010)
What is an
octane number, and what does it mean
? And what octane rating do you
? And what is that knocking sound that keeps coming out of your
engine?!! Seriously though, those types of questions are commonly asked by
anyone when they first get started in motorsports, and rightly
so. Here are the answers.
What is Octane Rating?
The octane rating of fuel that you see at the gas
pump is actually the Anti Knock Index
number, which is a
measurement of the anti-knocking properties of the fuel. It is the average of
two octane numbers, the RON (Research Octane Number)
MON (Motor Octane Number)
. The RON number determines
the low to medium-speed knock while the MON number determines the high-speed and
partial throttle heavy load knock characteristics. The higher the Anti Knock
Index number the better the fuel is to resisting premature detonation, or engine
knock. In other words, lower octane fuel is actually more
than higher-octane fuel.
What's the risk?
Abnormal combustion can cause knocking or pinging
sounds to come from your engine. This means that the gas that you are using is
either burning uncontrollably in the combustion chamber (often referred to as
detonation) or the fuel is being ignited prematurely by other sources such as a
glowing fragment of carbon in the cylinder instead of waiting for the spark from
the spark plug (this is called pre-ignition). Obviously, any
explosion that occurs before the piston reaches the top of it's rotation is
going to work against the engine, not for it. So it is important to
have a gasoline that will not burn either uncontrollably or prematurely.
Should I Be Buying Race Gas?
If you are racing, and have a modified
motor with very a high compression ratio, you might find the need to go for a
very high-octane fuel. But like most things, wait until it poses a
problem, and then correct the problem. If you are like most people,
you don't have a “factory bike”, you have a bike from the
factory. The engineers at the motorcycle factory have designed, built
and tested your bike so it would run well on pump gas. Stick with
premium pump gas, like it says in the manual and you'll do great.